Coordination protocol between dispersed storage processing units and rebuild modules

ABSTRACT

Methods and apparatus for use in a dispersed storage network (DSN) to facilitate coordination between dispersed storage computing devices and dispersed storage integrity processing unit rebuild modules. In one example, data may be rebuilt in a DSN by determining a rebuild task to be executed based on an attempt to access data in the DSN. Status information regarding the rebuild task is then generated and forwarded to the dispersed storage computing device and/or one or more dispersed storage units for subsequent attempts to access data in the DSN.

CROSS REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility Patent Applications claims priority pursuant to 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/314,839, filed 29 Mar. 2016, entitled “PROCESSING AN ENCODED DATA SLICE IN A DISPERSED STORAGE NETWORK,” which is hereby incorporated herein by reference in its entirety and made part of the present U.S. Utility Patent Applications for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks, and more particularly to cloud storage.

Description of Related Art

Computing devices are known to communicate data, process data, and/or store data. Such computing devices range from wireless smart phones, laptops, tablets, personal computers (PC), work stations, and video game devices, to data centers that support millions of web searches, stock trades, or on-line purchases every day. In general, a computing device includes a central processing unit (CPU), a memory system, user input/output interfaces, peripheral device interfaces, and an interconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using “cloud computing” to perform one or more computing functions (e.g., a service, an application, an algorithm, an arithmetic logic function, etc.) on behalf of the computer. Further, for large services, applications, and/or functions, cloud computing may be performed by multiple cloud computing resources in a distributed manner to improve the response time for completion of the service, application, and/or function. For example, Hadoop is an open source software framework that supports distributed applications enabling application execution by thousands of computers.

In addition to cloud computing, a computer may use “cloud storage” as part of its memory system. As is known, cloud storage enables a user, via its computer, to store files, applications, etc. on a remote storage system. The remote storage system may include a RAID (redundant array of independent disks) system and/or a dispersed storage system that uses an error correction scheme to encode data for storage.

In a RAID system, a RAID controller adds parity data to the original data before storing it across an array of disks. The parity data is calculated from the original data such that the failure of a single disk typically will not result in the loss of the original data. While RAID systems can address certain memory device failures, these systems may suffer from effectiveness, efficiency and security issues. For instance, as more disks are added to the array, the probability of a disk failure rises, which may increase maintenance costs. When a disk fails, for example, it needs to be manually replaced before another disk(s) fails and the data stored in the RAID system is lost. To reduce the risk of data loss, data on a RAID device is often copied to one or more other RAID devices. While this may reduce the possibility of data loss, it also raises security issues since multiple copies of data may be available, thereby increasing the chances of unauthorized access. In addition, co-location of some RAID devices may result in a risk of a complete data loss in the event of a natural disaster, fire, power surge/outage, etc.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, or distributed, storage network (DSN) in accordance with the present disclosure;

FIG. 2 is a schematic block diagram of an embodiment of a computing core in accordance with the present disclosure;

FIG. 3 is a schematic block diagram of an example of dispersed storage error encoding of data in accordance with the present disclosure;

FIG. 4 is a schematic block diagram of a generic example of an error encoding function in accordance with the present disclosure;

FIG. 5 is a schematic block diagram of a specific example of an error encoding function in accordance with the present disclosure;

FIG. 6 is a schematic block diagram of an example of slice naming information for an encoded data slice (EDS) in accordance with the present disclosure;

FIG. 7 is a schematic block diagram of an example of dispersed storage error decoding of data in accordance with the present disclosure;

FIG. 8 is a schematic block diagram of a generic example of an error decoding function in accordance with the present disclosure;

FIG. 9 is a schematic block diagram of an example of a dispersed storage network in accordance with the present disclosure;

FIG. 10A is a schematic diagram of another examples of a dispersed storage network in accordance with the present disclosure; and

FIG. 10B is a schematic diagram of an example of coordination between dispersed storage processing units and rebuild modules in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, or distributed, storage network (DSN) 10 that includes a plurality of dispersed storage (DS) computing devices or processing units 12-16, a managing unit 18, an integrity processing unit 20, and a DSN memory 22. The components of the DSN 10 are coupled to a network 24, which may include one or more wireless and/or wire lined communication systems; one or more non-public intranet systems and/or public internet systems; and/or one or more local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of dispersed storage units 36 (DS units) that may be located at geographically different sites (e.g., one in Chicago, one in Milwaukee, etc.), at a common site, or a combination thereof. For example, if the DSN memory 22 includes eight dispersed storage units 36, each storage unit is located at a different site. As another example, if the DSN memory 22 includes eight storage units 36, all eight storage units are located at the same site. As yet another example, if the DSN memory 22 includes eight storage units 36, a first pair of storage units are at a first common site, a second pair of storage units are at a second common site, a third pair of storage units are at a third common site, and a fourth pair of storage units are at a fourth common site. Note that a DSN memory 22 may include more or less than eight storage units 36.

Each of the DS computing devices 12-16, the managing unit 18, and the integrity processing unit 20 include a computing core 26, and network or communications interfaces 30-33 which can be part of or external to computing core 26. DS computing devices 12-16 may each be a portable computing device and/or a fixed computing device. A portable computing device may be a social networking device, a gaming device, a cell phone, a smart phone, a digital assistant, a digital music player, a digital video player, a laptop computer, a handheld computer, a tablet, a video game controller, and/or any other portable device that includes a computing core. A fixed computing device may be a computer (PC), a computer server, a cable set-top box, a satellite receiver, a television set, a printer, a fax machine, home entertainment equipment, a video game console, and/or any type of home or office computing equipment. Note that each of the managing unit 18 and the integrity processing unit 20 may be separate computing devices, may be a common computing device, and/or may be integrated into one or more of the computing devices 12-16 and/or into one or more of the dispersed storage units 36.

Each interface 30, 32, and 33 includes software and hardware to support one or more communication links via the network 24 indirectly and/or directly. For example, interface 30 supports a communication link (e.g., wired, wireless, direct, via a LAN, via the network 24, etc.) between computing devices 14 and 16. As another example, interface 32 supports communication links (e.g., a wired connection, a wireless connection, a LAN connection, and/or any other type of connection to/from the network 24) between computing devices 12 and 16 and the DSN memory 22. As yet another example, interface 33 supports a communication link for each of the managing unit 18 and the integrity processing unit 20 to the network 24.

Computing devices 12 and 16 include a dispersed storage (DS) client module 34, which enables the computing device to dispersed storage error encode and decode data (e.g., data object 40) as subsequently described with reference to one or more of FIGS. 3-8. In this example embodiment, computing device 16 functions as a dispersed storage processing agent for computing device 14. In this role, computing device 16 dispersed storage error encodes and decodes data on behalf of computing device 14. With the use of dispersed storage error encoding and decoding, the DSN 10 is tolerant of a significant number of storage unit failures (the number of failures is based on parameters of the dispersed storage error encoding function) without loss of data and without the need for a redundant or backup copies of the data. Further, the DSN 10 stores data for an indefinite period of time without data loss and in a secure manner (e.g., the system is very resistant to unauthorized attempts at accessing the data).

In operation, the managing unit 18 performs DS management services. For example, the managing unit 18 establishes distributed data storage parameters (e.g., vault creation, distributed storage parameters, security parameters, billing information, user profile information, etc.) for computing devices 12-16 individually or as part of a group of user devices. As a specific example, the managing unit 18 coordinates creation of a vault (e.g., a virtual memory block associated with a portion of an overall namespace of the DSN) within the DSN memory 22 for a user device, a group of devices, or for public access and establishes per vault dispersed storage (DS) error encoding parameters for a vault. The managing unit 18 facilitates storage of DS error encoding parameters for each vault by updating registry information of the DSN 10, where the registry information may be stored in the DSN memory 22, a computing device 12-16, the managing unit 18, and/or the integrity processing unit 20. The DS error encoding parameters (e.g., or dispersed storage error coding parameters) include data segmenting information (e.g., how many segments data (e.g., a file, a group of files, a data block, etc.) is divided into), segment security information (e.g., per segment encryption, compression, integrity checksum, etc.), error coding information (e.g., pillar width, decode threshold, read threshold, write threshold, etc.), slicing information (e.g., the number of encoded data slices that will be created for each data segment); and slice security information (e.g., per encoded data slice encryption, compression, integrity checksum, etc.).

The managing unit 18 creates and stores user profile information (e.g., an access control list (ACL)) in local memory and/or within memory of the DSN memory 22. The user profile information includes authentication information, permissions, and/or the security parameters. The security parameters may include encryption/decryption scheme, one or more encryption keys, key generation scheme, and/or data encoding/decoding scheme.

The managing unit 18 creates billing information for a particular user, a user group, a vault access, public vault access, etc. For instance, the managing unit 18 tracks the number of times a user accesses a non-public vault and/or public vaults, which can be used to generate per-access billing information. In another instance, the managing unit 18 tracks the amount of data stored and/or retrieved by a user device and/or a user group, which can be used to generate per-data-amount billing information.

As another example, the managing unit 18 performs network operations, network administration, and/or network maintenance. Network operations includes authenticating user data allocation requests (e.g., read and/or write requests), managing creation of vaults, establishing authentication credentials for user devices, adding/deleting components (e.g., user devices, storage units, and/or computing devices with a DS client module 34) to/from the DSN 10, and/or establishing authentication credentials for the storage units 36. Network operations can further include monitoring read, write and/or delete communications attempts, which attempts could be in the form of requests. Network administration includes monitoring devices and/or units for failures, maintaining vault information, determining device and/or unit activation status, determining device and/or unit loading, and/or determining any other system level operation that affects the performance level of the DSN 10. Network maintenance includes facilitating replacing, upgrading, repairing, and/or expanding a device and/or unit of the DSN 10.

To support data storage integrity verification within the DSN 10, the integrity processing or verification unit 20 (and/or other devices in the DSN 10 such as managing unit 18) may assess and perform rebuilding of ‘bad’ or missing encoded data slices. At a high level, the integrity processing unit 20 performs rebuilding by periodically attempting to retrieve/list encoded data slices, and/or slice names of the encoded data slices, from the DSN memory 22. Retrieved encoded slices are assessed and checked for errors due to data corruption, outdated versioning, etc. If a slice includes an error, it is flagged as a ‘bad’ or ‘corrupt’ slice. Encoded data slices that are not received and/or not listed may be flagged as missing slices. Bad and/or missing slices may be subsequently rebuilt using other retrieved encoded data slices that are deemed to be good slices in order to produce rebuilt slices. A multi-stage decoding process may be employed in certain circumstances to recover data even when the number of valid encoded data slices of a set of encoded data slices is less than a relevant decode threshold number. The rebuilt slices may then be written to DSN memory 22. Note that the integrity processing unit 20 may be a separate unit as shown, included in DSN memory 22, included in the computing device 16, managing unit 18, stored on a DS unit 36, and/or distributed among multiple storage units 36.

FIG. 2 is a schematic block diagram of an embodiment of a computing core 26 that includes a processing module 50, a memory controller 52, main memory 54, a video graphics processing unit 55, an input/output (IO) controller 56, a peripheral component interconnect (PCI) interface 58, an IO interface module 60, at least one IO device interface module 62, a read only memory (ROM) basic input output system (BIOS) 64, and one or more memory interface modules. The one or more memory interface module(s) includes one or more of a universal serial bus (USB) interface module 66, a host bus adapter (HBA) interface module 68, a network interface module 70, a flash interface module 72, a hard drive interface module 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). The DSN interface module 76 and/or the network interface module 70 may function as one or more of the interface 30-33 of FIG. 1. Note that the IO device interface module 62 and/or the memory interface modules 66-76 may be collectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storage error encoding of data. When a computing device 12 or 16 has data to store it disperse storage error encodes the data in accordance with a dispersed storage error encoding process based on dispersed storage error encoding parameters. The dispersed storage error encoding parameters include an encoding function (e.g., information dispersal algorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding, non-systematic encoding, on-line codes, etc.), a data segmenting protocol (e.g., data segment size, fixed, variable, etc.), and per data segment encoding values. The per data segment encoding values include a total, or pillar width, number (T) of encoded data slices per encoding of a data segment (i.e., in a set of encoded data slices); a decode threshold number (D) of encoded data slices of a set of encoded data slices that are needed to recover the data segment; a read threshold number (R) of encoded data slices to indicate a number of encoded data slices per set to be read from storage for decoding of the data segment; and/or a write threshold number (W) to indicate a number of encoded data slices per set that must be accurately stored before the encoded data segment is deemed to have been properly stored. The dispersed storage error encoding parameters may further include slicing information (e.g., the number of encoded data slices that will be created for each data segment) and/or slice security information (e.g., per encoded data slice encryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as the encoding function (a generic example is shown in FIG. 4 and a specific example is shown in FIG. 5); the data segmenting protocol is to divide the data object into fixed sized data segments; and the per data segment encoding values include: a pillar width of 5, a decode threshold of 3, a read threshold of 4, and a write threshold of 4. In accordance with the data segmenting protocol, the computing device 12 or 16 divides the data (e.g., a file (e.g., text, video, audio, etc.), a data object, or other data arrangement) into a plurality of fixed sized data segments (e.g., 1 through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more). The number of data segments created is dependent of the size of the data and the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a data segment using the selected encoding function (e.g., Cauchy Reed-Solomon) to produce a set of encoded data slices. FIG. 4 illustrates a generic Cauchy Reed-Solomon encoding function, which includes an encoding matrix (EM), a data matrix (DM), and a coded matrix (CM). The size of the encoding matrix (EM) is dependent on the pillar width number (T) and the decode threshold number (D) of selected per data segment encoding values. To produce the data matrix (DM), the data segment is divided into a plurality of data blocks and the data blocks are arranged into D number of rows with Z data blocks per row. Note that Z is a function of the number of data blocks created from the data segment and the decode threshold number (D). The coded matrix is produced by matrix multiplying the data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encoding with a pillar number (T) of five and decode threshold number of three. In this example, a first data segment is divided into twelve data blocks (D1-D12). The coded matrix includes five rows of coded data blocks, where the first row of X11-X14 corresponds to a first encoded data slice (EDS 1_1), the second row of X21-X24 corresponds to a second encoded data slice (EDS 2_1), the third row of X31-X34 corresponds to a third encoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to a fourth encoded data slice (EDS 4_1), and the fifth row of X51-X54 corresponds to a fifth encoded data slice (EDS 5_1). Note that the second number of the EDS designation corresponds to the data segment number. In the illustrated example, the value X11=aD1+bD5+cD9, X12=aD2+bD6+cD10, . . . X53=mD3+nD7+oD11, and X54=mD4+nD8+oD12.

Returning to the discussion of FIG. 3, the computing device also creates a slice name (SN) for each encoded data slice (EDS) in the set of encoded data slices. A typical format for a slice name 80 is shown in FIG. 6. As shown, the slice name (SN) 80 includes a pillar number of the encoded data slice (e.g., one of 1-T), a data segment number (e.g., one of 1-Y), a vault identifier (ID), a data object identifier (ID), and may further include revision level information of the encoded data slices. The slice name functions as at least part of a DSN address for the encoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces a plurality of sets of encoded data slices, which are provided with their respective slice names to the storage units for storage. As shown, the first set of encoded data slices includes EDS 1_1 through EDS 5_1 and the first set of slice names includes SN 1_1 through SN 5_1 and the last set of encoded data slices includes EDS 1_Y through EDS 5_Y and the last set of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storage error decoding of a data object that was dispersed storage error encoded and stored in the example of FIG. 4. In this example, the computing device 12 or 16 retrieves from the storage units at least the decode threshold number of encoded data slices per data segment. As a specific example, the computing device retrieves a read threshold number of encoded data slices.

In order to recover a data segment from a decode threshold number of encoded data slices, the computing device uses a decoding function as shown in FIG. 8. As shown, the decoding function is essentially an inverse of the encoding function of FIG. 4. The coded matrix includes a decode threshold number of rows (e.g., three in this example) and the decoding matrix in an inversion of the encoding matrix that includes the corresponding rows of the coded matrix. For example, if the coded matrix includes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2, and 4, and then inverted to produce the decoding matrix.

FIG. 9 is a diagram of an example of a dispersed storage network. The dispersed storage network includes a DS (dispersed storage) client module 34 (which may be in DS computing devices 12 and/or 16 of FIG. 1), a network 24, and a plurality of DS units 36-1 . . . 36-n (which may be storage units 36 of FIG. 1 and which form at least a portion of DS memory 22 of FIG. 1), a DSN managing unit (not shown—device 18 in FIG. 1), and a DS integrity verification module or unit 20. The DS client module 34 includes an outbound DS processing section 81 and an inbound DS processing section 82. Each of the DS units 36-1 . . . 36-n includes a controller 86, a processing module 84 including a communications interface for communicating over network 24 (not shown), memory 88, a DT (distributed task) execution module 90, and a DS client module 34.

In an example of operation, the DS client module 34 receives data 92. The data 92 may be of any size and of any content, where, due to the size (e.g., greater than a few Terabytes), the content (e.g., secure data, etc.), and/or concerns over security and loss of data, distributed storage of the data is desired. For example, the data 92 may be one or more digital books, a copy of a company's emails, a large-scale Internet search, a video security file, one or more entertainment video files (e.g., television programs, movies, etc.), data files, and/or any other large amount of data (e.g., greater than a few Terabytes). Within the DS client module 34, the outbound DS processing section 81 receives the data 92. The outbound DS processing section 81 processes the data 92 to produce slice groupings 96. As an example of such processing, the outbound DS processing section 81 partitions the data 92 into a plurality of data partitions. For each data partition, the outbound DS processing section 81 dispersed storage (DS) error encodes the data partition to produce encoded data slices and groups the encoded data slices into a slice grouping 96.

The outbound DS processing section 81 then sends, via the network 24, the slice groupings 96 to the DS units 36-1 . . . 36-n of the DSN memory 22 of FIG. 1. For example, the outbound DS processing section 81 sends slice group to DS storage unit 36-1. As another example, the outbound DS processing section 81 sends slice group #n to DS unit #n.

In one example of operation, the DS client module 34 requests retrieval of stored data within the memory of the DS units 36. In this example, the task 94 is retrieve data stored in the DSN memory 22. Accordingly, and according to one embodiment, the outbound DS processing section 81 converts the task 94 into a plurality of partial tasks 98 and sends the partial tasks 98 to the respective DS storage units 36-1 . . . 36-n.

In response to the partial task 98 of retrieving stored data, a DS storage unit 36 identifies the corresponding encoded data slices 99 and retrieves them. For example, DS unit #1 receives partial task #1 and retrieves, in response thereto, retrieved slices #1. The DS units 36 send their respective retrieved slices 99 to the inbound DST processing section 82 via the network 24.

The inbound DS processing section 82 converts the retrieved slices 99 into data 92. For example, the inbound DS processing section 82 de-groups the retrieved slices 99 to produce encoded slices per data partition. The inbound DS processing section 82 then DS error decodes the encoded slices per data partition to produce data partitions. The inbound DS processing section 82 de-partitions the data partitions to recapture the data 92.

According to one example, a coordination protocol is established between DS computing devices or processing units (12 and 16 of FIG. 1)/DS client modules 34 (FIGS. 1 and 9) servicing DSN access requests, and rebuild modules 27 (which are part of computing core 26 of integrity processing units 20) repairing data stored on DS units 36-1 . . . 36-n within that DSN memory, that enables several reliability and performance improvements. DS processing units 12 and 16 may learn of unhealthy, outdated, or missing data in several ways including:

1. When a DS processing unit attempts to write slices to one or more of a set of DS units or a set of primary DS units, but fails to write the desired number of slices;

2. When a DS processing unit writes more than the desired number of slices to one or more of a set of DS units or a set of primary DS units, or writes slices to non-primary DS units or locations;

3. When a DS processing unit attempts to read slices from one or more of a set of DS units or a set of primary DS units, and determines that some of the returned slices were missing or of an incorrect revision; or

4. When a DS processing unit attempts to reassemble data from one or more of a set of DS units or a set of primary DS units, and finds that at least one of the slices is corrupted or otherwise cannot be used to correctly reassemble the source data.

In each of these cases, a DS processing unit 12 or 16 may become aware of a data health problem before any rebuild module 27 detects it. When this occurs, the DS processing unit 12 or 16 may send a notification message to at least one rebuild module 27 informing it of the afflicted slices, and the error condition that applies. Alternately, the DS processing unit 12 or 16 may store an entry into a rebuild queue (which may itself be implemented a dispersed data structure (such as a DLCI) stored within the DSN memory). Rebuild modules 27 may query this queue to find rebuild tasks. Another hint that the DS processing units 12 or 16 can provide to rebuild modules 27 is when the DS processing unit 12 or 16 discovers a DS unit 36 is unreachable or unavailable. The DS processing 12 or 16 unit may notify rebuild modules 27 of this outage, such that rebuild modules can focus on checking the health of the slices on this DS unit 36 when it returns. Slices may have been lost as part of the event triggering the outage, and furthermore, the DS unit 36 may miss slices that other DS processing units 12 or 16 attempted to write, update, or delete. These notifications from the DS processing unit 12 or 16, enhance the efficiency and speed of the rebuild modules in repairing data, and thereby increase reliability.

Similarly, rebuild modules 27 may detect conditions and learn information that if provided to DS processing units 12 or 16, could increase performance and reduce latency, among other things. Some of this information includes:

1. When a rebuild module determines that a DS unit is undergoing a high rebuilding load;

2. When a rebuild module determines that a DS unit has a higher fraction of missing or outdated slices than most of its peers (and what this fraction is); and

3. When a rebuild module determines a range of the namespace that is unhealthy, slow, is missing many or most slices, or is entirely unavailable (e.g. due to a memory device having been “quarantined”).

This information, if made available to DS processing units 12 or 16, could greatly enhance the performance of DS processing units 12 or 16 in a number of ways. If a DS processing unit 12 or 16 knows that a DS unit 36 is undergoing a high level of rebuilding, it may preferentially avoid issuing access requests to that devices, in order to achieve higher performance, and also to not disrupt the rebuild efforts (enabling the rebuild to complete faster). Similarly, when the DS processing unit 12 or 16 knows a particular range is unhealthy, slow, or is missing many slices, it can factor this information in to its read-ranking, and pessimistic reads, and other smart-read algorithms to preferentially avoid sending requests to those identified ranges. This avoids wasted round-trips, network IO, and processing. Using a coordination protocol between DS processing units 12 and 16 and rebuild modules, both are able to take advantage of information that the other entity discovers.

Further explanations of examples of such coordination protocols for rebuilding data in a dispersed storage network are set out below in conjunction with FIGS. 10A and 10B.

FIG. 10A is a schematic block diagram of another embodiment of a dispersed storage network that includes the computing device 16 of FIG. 1, the network 24 of FIG. 1, the DS integrity processing unit 20 of FIGS. 1 and 9, and a set of storage units 36-1 . . . 36-n (labelled 36-1 . . . 36-n in FIG. 10A) which may be storage units 36 of FIG. 1 and which form at least a portion of DS memory 22 of FIG. 1). Each DS unit includes a processing module 84 (labelled 84-1, 84-2 . . . 84-n for DS units 36-1, 36-2 . . . 36-n respectively) and at least one memory 88 (labelled 88-1, 88-2 . . . 88-n for DS units 36-1, 36-2 . . . 36-n respectively). Each processing module may be implemented utilizing the processing module 84 of FIG. 9. Each memory may be implemented utilizing the memory 88 of FIG. 9. Hereafter, the set of storage units may be interchangeably referred to as a set of DS units. The DSN functions to rebuild data in DS units 36.

An example of operation of the optimizing of the DSN, while accessing encoded data slices of the set of DS units 36, the DS processing unit 16 generates rebuild task information based on accessing, or an attempt to access, one or more of a set of DS units 36-1 . . . 36-n. The generating includes one or more of detecting a slice access error following an attempt to access one or more of DS units 36-1 . . . 36-n (including a write failure, a read failure, detecting a missing data slice or slices, detecting a corrupt data slice or slices, detecting a missing revision of the slice, detecting an off-line DS unit, etc.), determining an identifier of an encoded data slice associated with the slice access error, determining a type of the slice access error, and generating the rebuild task information to include one or more of a rebuild task, identifier, a type, a DS unit status, a prioritization scheme, and a priority level for rebuilding.

Having generated the rebuild task information, the DS processing unit 16 sends, via the network 24, the rebuild task information to the DS integrity processing unit 20. For example, the DS processing unit 16 generates and sends rebuild task information 100 for receipt by the DS integrity processing unit 20, where the rebuild task information 100 corresponds to the encoded data slices for rebuilding associated with one or more of the DS units 36-1 . . . 36-n. Alternatively, the rebuild task information 100 can be received from one or more of DS units 36-1 . . . 36-n.

The DS integrity processing unit 20 determines a rebuild task to execute based on rebuild task information and executes the one or more rebuild tasks. The determining includes determining a prioritization for one or more rebuild tasks, associating a timeframe with execution of the rebuild tasks (e.g., waiting until an off-line DS unit becomes online again to perform slice health checks), and facilitating execution of a rebuild task and an associated timeframe.

Prior to, or while, executing the one or more rebuild tasks, the DS integrity processing unit 20 generates DS unit status information 102, associated with the one or more rebuild tasks and/or one or more DS units 36-1 . . . 36-n. The generating includes determining a level of rebuilding loading, determining the level of storage errors within one or more DS units, determining that a range of data slices is unhealthy (e.g., slow response, missing many slices, etc.), generating the storage unit status information to include an identifier for one or more of the DS units, an identifier of an individual slice, an identifier of range of slices associated with a storage error, and an activity level indicator, etc. For the example, the DS integrity processing unit 20 generates storage unit status information 102 associated with the status of one or more of the DS units 36-1 . . . 36-n. Having generated the storage unit status information, the DS integrity processing unit 20 sends or forwards, via the network 24, the storage unit status information to DS processing unit 16 and/or one or more of the DS units 36-1 . . . 36-n.

When subsequently accessing, or attempting to access, one or more DS units of the set of DS units 36-1 . . . 36-n, the DS processing unit 16 performs the accessing, or attempt to access, in accordance with the storage unit status information 102. For example, the DS processing unit 16 avoids utilizing storage units associated with heavy rebuilding activities, avoids utilizing storage units associated with numerous slice errors, and avoids accessing encoded data slices associated with too many storage errors, etc.

FIG. 10B is a flowchart illustrating an example of optimizing dispersed storage network performance. The method includes a step 1000 where a DS client module 34 of FIG. 9 (accessing module) of computing device 12 or 16 in FIGS. 1 and 10A, while accessing encoded data slices with one or more of a set of DS units, generates rebuild task information based on the accessing. The generating includes one or more of detecting a slice access error, determining an identifier of an encoded data slice associated with the slice access error, determining a type of the slice access error, generating the rebuild task information to include one or more of a rebuild task, a data slice identifier, a type of slice access error, a DS unit status, a DS unit identifier, a prioritization scheme, and a priority level for an encoded data slice rebuilding operation.

The method continues at the step 1010 where the accessing module sends the rebuild task information to a rebuilding or rebuild module 27 (e.g. in computing core 26 of DS integrity processing unit 20 in FIG. 10A). The sending includes at least one of transmitting the rebuild task information directly to the rebuilding module and storing the rebuild task information as a set of rebuild task slices in a set of DS units (e.g. 36-1 . . . 36-n of FIG. 10A), as a rebuilding mailbox, for subsequent rebuild task slice retrieval and recovery of the rebuild task information by the rebuilding module 27.

The method continues at the step 1020 where the rebuilding module 27 executes one or more rebuilding tasks in accordance with the rebuild task information. The executing includes one or more of determining a prioritization for one or more rebuilding tasks, associating a timeframe with execution of the rebuilding tasks, and facilitating the execution of a particular rebuilding task within an associated time frame.

While executing one or more rebuilding tasks, the method continues at the step 1030 where the rebuilding module 27 generates storage unit status information for one or more rebuild tasks and/or one or more of the set of storage units 36-1 . . . 36-n. The generating includes one or more of determining a level of rebuilding loading, determining a level of storage errors within a DS unit, determining that a range of encoded data slices is unhealthy, and generating the storage unit status information to include identifiers for one or more of the DS units, an individual slice associated with a storage error, a range of slices associated with a storage error, and an activity level indicator.

The method continues at the step 1040 where the rebuilding module 27 sends the storage unit status information to the accessing module of DS computing device 16. The sending includes at least one of directly sending the status information to the accessing module and temporarily storing the storage unit status information in a DS unit, or a set of DS units, as a set of storage unit status slices (e.g., a status mailbox), for subsequent retrieval and recovery of the status information by the accessing module.

When subsequently accessing the set of DS units, the method continues at the step 1050 where the accessing module performs the accessing in accordance with the storage unit status information. As examples of the accessing in accordance with the storage unit status information, the accessing module avoids utilizing DS units associated with heavy rebuilding activities, avoids utilizing DS units associated with numerous slice errors, and avoids accessing encoded data slices associated with too many storage errors.

The methods described above in conjunction with the computing device and the storage units can alternatively be performed by other modules of the dispersed storage network or by other devices. For example, any combination of a first module, a second module, a third module, a fourth module, etc. of the computing device and the storage units may perform the method described above. In addition, at least one memory section (e.g., a first memory section, a second memory section, a third memory section, a fourth memory section, a fifth memory section, a sixth memory section, etc. of a non-transitory computer readable storage medium) that stores operational instructions can, when executed by one or more processing modules of one or more computing devices and/or by the storage units of the dispersed storage network (DSN), cause the one or more computing devices and/or the storage units to perform any or all of the method steps described above.

As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “configured to”, “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for an example of indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “configured to”, “operable to”, “coupled to”, or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal A has a greater magnitude than signal B, a favorable comparison may be achieved when the magnitude of signal A is greater than that of signal B or when the magnitude of signal B is less than that of signal A. As may be used herein, the term “compares unfavorably”, indicates that a comparison between two or more items, signals, etc., fails to provide the desired relationship.

As may also be used herein, the terms “processing module”, “processing circuit”, “processor”, and/or “processing unit” may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module, module, processing circuit, and/or processing unit may be, or further include, memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of another processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the Figures. Such a memory device or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claims. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claims. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.

In addition, a flow diagram may include a “start” and/or “continue” indication. The “start” and “continue” indications reflect that the steps presented can optionally be incorporated in or otherwise used in conjunction with other routines. In this context, “start” indicates the beginning of the first step presented and may be preceded by other activities not specifically shown. Further, the “continue” indication reflects that the steps presented may be performed multiple times and/or may be succeeded by other activities not specifically shown. Further, while a flow diagram indicates a particular ordering of steps, other orderings are likewise possible provided that the principles of causality are maintained.

The one or more embodiments are used herein to illustrate one or more aspects, one or more features, one or more concepts, and/or one or more examples. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from Figure to Figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones.

Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of the embodiments. A module implements one or more functions via a device such as a processor or other processing device or other hardware that may include or operate in association with a memory that stores operational instructions. A module may operate independently and/or in conjunction with software and/or firmware. As also used herein, a module may contain one or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes one or more memory elements. A memory element may be a separate memory device, multiple memory devices, or a set of memory locations within a memory device. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. The memory device may be in a form a solid state memory, a hard drive memory, cloud memory, thumb drive, server memory, computing device memory, and/or other physical medium for storing digital information. A computer readable memory/storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

While particular combinations of various functions and features of the one or more embodiments have been expressly described herein, other combinations of these features and functions are likewise possible. The present disclosure is not limited by the particular examples disclosed herein and expressly incorporates these other combinations. 

What is claimed is:
 1. A method for rebuilding data in a dispersed storage network, the dispersed storage network including a plurality of dispersed storage units storing encoded data slices, a dispersed storage (DS) processing unit for accessing the encoded data slices in the plurality of dispersed storage units, and an integrity processing unit remote from the DS processing unit and the dispersed storage units for rebuilding the encoded data slices at the plurality of dispersed storage units, the method comprises: attempting, by the DS processing unit, to access one or more encoded data slices of a first dispersed storage unit of the plurality of dispersed storage units during a read or write operation; receiving, by the DS processing unit, information about a data health problem associated with the first dispersed storage unit of the plurality of dispersed storage units, wherein the data health problem is determined by recognition, by the DS processing unit, of an error occurring during the attempting to access the one or more encoded data slices; generating, by the DS processing unit, rebuild task information based on the information about a data health problem, the rebuild task information including a notification of afflicted encoded data slices of the one or more encoded data slices as well as information about the error occurring during the attempting to access the one or more encoded data slices; sending, by the DS processing unit, a notification message directly to a rebuilding module of the integrity processing unit, the notification message including the rebuild task information, wherein the integrity processing unit determines a rebuilding task to execute based on the rebuild task information prior to the integrity processing unit detecting the data health problem; and receiving, by the DS processing unit, storage unit status information generated by the integrity processing unit and associated with the first dispersed storage unit of the plurality of dispersed storage units, wherein the storage unit status information is associated with a rebuild task to be executed based on the rebuild task information; determining, by the DS processing unit, at least one rebuilding activity at the plurality of dispersed storage units based on the received storage units status information; and selectively issuing, by the DS processing unit, access requests to one of more of the plurality of dispersed storage units based on the rebuilding activity.
 2. The method of claim 1, wherein the rebuild task information includes at least one selected from the group consisting of a data slice identifier, a type of slice access error, a dispersed storage unit status, a dispersed storage unit identifier, a prioritization scheme, and a priority level.
 3. The method of claim 1, wherein the error includes at least one selected from the group consisting of a write failure, a read failure, a detecting of a missing data slice, a detecting of a corrupt data slice, a detecting of a missing data slice revision, and a detecting of one or more of the plurality of dispersed storage units being offline.
 4. The method of claim 1, wherein the storage unit status information associated with the first dispersed storage unit of the plurality of dispersed storage units includes one or more of an identifier of the first dispersed storage unit, an identifier of an individual slice stored on the first dispersed storage unit, an identifier of a range of slices stored on the first dispersed storage unit, and an activity level indicator.
 5. A dispersed storage integrity verification unit for rebuilding data in a dispersed storage network, the dispersed storage network including a plurality of dispersed storage units storing encoded data slices, and a dispersed storage (DS) processing unit remote from the dispersed storage integrity verification unit for accessing the encoded data slices in the plurality of dispersed storage units, the dispersed storage integrity verification unit comprising: a communications interface; a memory; and a processor; wherein the memory includes instructions for causing the processor to: receive, from a dispersed storage (DS) processing unit, rebuild task information including a notification of afflicted encoded data slices of one or more encoded data slices as well as information about an error occurring during an attempt of the DS processing unit to access one or more encoded data slices during a read or write operation to a dispersed storage unit of the plurality of dispersed storage units, wherein the notification is received prior to detection of the afflicted encoded data slices by the dispersed storage integrity verification unit; determine a first rebuild task to rebuild and store, in one or more of the plurality of dispersed storage units, the afflicted encoded data slices based on the rebuild task information; generate storage unit status information associated with the first rebuild task to be executed; forward, from the dispersed storage integrity verification unit to the DS processing unit, the storage unit status information associated with the first dispersed storage unit of the plurality of dispersed storage units; and execute the first rebuild task.
 6. The dispersed storage integrity verification unit of claim 5, wherein the rebuild task information includes one or more of a data slice identifier, a type of slice access error, a dispersed storage unit status, a dispersed storage unit identifier, a prioritization scheme, or a priority level.
 7. The dispersed storage integrity verification unit of claim 5, wherein the error includes at least one selected from the group consisting of a write failure, a read failure, a detecting of a missing data slice, a detecting of a corrupt data slice, a detecting of a missing data slice revision, and a detecting of one or more of the plurality of dispersed storage units being offline.
 8. The dispersed storage integrity verification unit of claim 5, wherein the memory further includes at least one selected from the group consisting of: instructions for causing the processor to determine a prioritization for executing the first rebuild task and a second rebuild task; instructions for causing the processor to associate a timeframe with the first rebuild task to be executed; and instructions for causing the processor to determine one or more of a level of rebuilding loading, a level of storage errors within the first dispersed storage unit, and a range of unhealthy data slices.
 9. The dispersed storage integrity verification unit of claim 5, wherein the storage unit status information associated with the first dispersed storage unit of the plurality of dispersed storage units includes at least one selected from the group consisting of an identifier of the first dispersed storage unit, an identifier of an individual slice stored on the first dispersed storage unit, an identifier of a range of slices stored the first dispersed storage unit, and an activity level indicator.
 10. The dispersed storage integrity verification unit of claim 5, wherein the memory further includes instructions for causing the processor to forward the storage unit status information to another of the plurality of dispersed storage units. 